In related art, on-rail detection of a train has been performed using a track circuit. While, in on-rail detection using a track circuit, it is possible to always detect whether a train is on rail or not on a ground side, there is a problem that it is troublesome and expensive to install and maintain the track circuit.
Meanwhile, in recent years, an on-rail detection method utilizing radio communication has been proposed. For example, a technique is known that detects on-rail of a train on a ground side by transmitting a location of an own train measured by the train to the ground side (see JP-A-2007-15517). In this JP-A-2007-15517, a base apparatus is provided for each predetermined section (base) of a track, on-rail of a train within the base is detected (managed), and, while the base apparatus is down, coming-in and going-out of the train between bases can be recognized by an ID being read from the train that passes through a boundary of the bases.
However, with the technique of JP-A-2007-15517, to prepare for a case where a base apparatus is down, it is necessary to provide an ID detection apparatus at a boundary location of each base. That is, the technique of JP-A-2007-15517 requires to provide train detection means different from radio communication on the ground.